The present invention is directed to a technique for use in a method of manufacture of a semiconductor device and to a semiconductor device produced by the method; and, more in particular, it relates to a technique that is effective when applied to a method of manufacturing a semiconductor device having buried wirings comprising copper as a main conductor layer and a semiconductor device.
A buried wiring structure is formed by burying a wiring material into wiring openings, such as wiring grooves or holes, formed in an insulative film, by use of the wiring forming technique referred to as a Damascene technique (Single-Damascene technique and Dual-Damascene technique).
However, when the main wiring material is made of copper, since copper tends to diffuse more into the insulative film compared with other metals, such as aluminum, the surface (bottom and the lateral side) of buried wirings typically is covered with a thin barrier metal film so that the buried wirings comprising copper are not in direct contact with the insulative film, thereby suppressing or preventing copper in the buried wirings from diffusing into the insulative film. Further, an insulative film for a wiring cap comprising, for example, a silicon nitride film is formed on the upper surface of an insulative film in which wiring openings are formed to cover the upper surface of the buried wirings, so that copper in the buried wirings is suppressed or prevented from diffusing from the upper surface of the buried wirings into the insulative film.
The Damascene wiring technique is described, for example, in Japanese Patent Laid-Open No. Hei 11 (1999)-233630, which discloses a technique in which an SiON film is used as the insulative film for a wiring cap. Further, Japanese Patent Laid-Open No. 2000-133710, for example, describes a technique in which a silicon nitride film of high Si content is used as the insulative film for a wiring cap. Further, Japanese Patent Laid-Open No. 2000-252286, for example, discloses a technique in which hydrogen atom-containing silicon is used as the insulative film for a wiring cap (dielectric constant xcex5=4). Further, Japanese Patent Laid-Open No. 2000-332102 discloses a technique in which a BCB film (xcex5=2.7) is used as the insulative film for a wiring cap. Further, Japanese Patent Laid-Open No. Hei 10(1998)-150105, for example, discloses a technique in which an organic low dielectric film (xcex5=2.3-2.6) is used as an insulative film for a wiring cap. Further, Japanese Patent Laid-Open No. Hei 11(1999)-243147, for example, discloses a technique in which an SION film is used as an inter-layer insulative film in a Damascene wiring structure.
In recent years, for attaining a high performance semiconductor device that is capable of high speed operation, a structure using copper as the main wiring material has been adopted, as described above, with an insulative film of low dielectric constant being used as the material for the insulative film in which the wiring openings are formed. According to a study by the present inventors, it is essential to use an insulative film of low dielectric constant also as a material for the insulative film for a wiring cap, as described above, in order to obtain a higher speed of operation.
In view of the above, the present inventors have examined the introduction of a silicon oxynitride film (SiON), with a dielectric constant that is lower than that of the silicon nitride film, as a material for the insulative film for a wiring cap. Also, it has been found for the first time by the present inventors that the technique of using a SiON film as the insulative film for a wiring cap involves the following considerations.
That is, since an oxygen-containing gas, such as N2O, is used for deposition of an SiON film, oxygen activated in the initial stage of film deposition directly hits on a barrier metal film that is exposed to the film deposition surface and oxidizes the exposed portion of the barrier metal film, so as to deteriorate the barrier property near the boundary between the insulative film for a wiring cap and the buried wirings, thereby to shorten the TDDB life.
An object of the present invention is to provide a technique that is capable of improving the dielectric breakdown strength between wirings using copper as a main conductor layer.
The foregoing and other objects, as well as novel features of this invention, will become apparent by a reading the descriptions in the present specification, with reference to the appended drawings.
Among the aspects of the present invention disclosed in this application, an outline of typical features of the invention will be briefly explained below.
That is, according to this invention, an insulative film for a wiring cap is formed such that a conductive barrier film of wirings comprising copper as the main wiring material is not oxidized.
This invention provides, as a first feature, a method of manufacture of a semiconductor device, comprising the following steps of:
(a) forming a wiring opening to a first insulative film deposited on a wafer;
(b) forming wirings in the wiring opening, the wirings including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient; and
(c) depositing a second insulative film for protecting the first conductor film against oxidation on the first insulative film and the wirings, and then depositing a third insulative film on the second insulative film by a chemical vapor deposition method using an oxygen-containing gas.
Preferably, the second insulative film comprises a silicon nitride film. Also, the second insulative film may comprise a silicon carbide film or a silicon carbonitride film. Preferably, the third insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture containing a trimethoxysilane gas and a nitrogen oxide gas. Preferably, the thickness of the second insulative film is less than that of the third insulative film.
This invention provides, as a second feature, a method of manufacture of a semiconductor device, comprising the following steps of:
(a) forming a wiring opening to a first insulative film deposited on a wafer;
(b) forming wirings in the wiring opening, the wirings including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient; and
(c) depositing a second insulative film on the first insulative film and the wirings under the condition that the first conductor film is not oxidized, and then depositing a third insulative film on the second insulative film by a chemical vapor deposition method using an oxygen-containing gas.
Preferably, the second insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture of a trimethoxysilane gas and a nitrogen gas or an ammonia gas. Preferably, the third insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture containing a trimethoxysilane gas and a nitrogen oxide gas.
This invention provides, as a third feature, a method of manufacture of a semiconductor device comprising the following steps of:
(a) forming a wiring opening to a first insulative film deposited on a wafer;
(b) forming wirings in the wiring opening, the wirings including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient; and
(c) depositing a second insulative film by a chemical vapor deposition method using a gas mixture containing an oxygen-containing gas and a dilution gas on the first insulative film and the wirings, and then depositing a third insulative film on the second insulative film by a chemical vapor deposition method using an oxygen-containing gas.
In the preferred embodiment, the second insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture containing a trimethoxysilane gas, an oxygen-containing gas and a dilution gas. Preferably, the dilution gas is a nitrogen gas or an ammonia gas. Preferably, the oxygen-containing gas used upon deposition of the second insulative film is oxygen or nitrogen oxide.
Preferably, the third insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture containing a trimethoxysilane gas and a nitrogen oxide gas.
Preferably, the second insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture containing a trimethoxysilane gas, an oxygen-containing gas and a dilution gas, and the third insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture containing a trimethoxysilane gas and a nitrogen oxide gas. Preferably, the thickness of the second insulative film is less than that of the third insulative film.
This invention provides, as a fourth feature, a method of manufacture of a semiconductor device, comprising the following steps of:
(a) forming a wiring opening to a first insulative film deposited on a wafer;
(b) forming wirings in the wiring opening, the wirings including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient;
(c) applying a reducing plasma processing to the wirings; and
(d) depositing a fourth insulative film on the first insulative film and the wirings;
wherein a first electric power applied to a first electrode holding the wafer is less than a second electric power applied to a second electrode opposed to the wafer or zero, in the reducing plasma processing.
In the preferred embodiment, the fourth insulative film comprises a single component film of a silicon oxynitride film formed by a plasma vapor deposition method using a gas mixture containing a trimethoxysilane gas and a nitrogen oxide gas. Preferably, the fourth insulative film has a fifth insulative film deposited on the wirings and the first insulative film and a sixth insulative film deposited thereon, and the fifth insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture of a trimethoxysilane gas and a nitrogen gas or an ammonia gas. Preferably, the sixth insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture containing a trimethoxysilane gas and a nitrogen oxide gas. Preferably, the thickness of the fifth insulative film is less than that of the sixth insulative film.
Preferably, the fourth insulative film has a fifth insulative film deposited on the wirings and the first insulative film and a sixth insulative film deposited thereon, and the fifth insulative film comprises a silicon oxynitride film formed by a chemical vapor deposition method using a gas mixture containing a trimethoxysilane, an oxygen-containing gas and a dilution gas. The dilution gas is a nitrogen gas or an ammonia gas. The oxygen-containing gas used upon formation of the fifth insulative film is oxygen or nitrogen oxide.
This invention provides, as a fifth feature, a method of manufacture of a semiconductor device comprising the following steps of:
(a) forming a wiring opening to a first insulative film deposited on a wafer;
(b) forming wirings in the wiring opening, the wirings having a height for the upper surface having a step relative to the upper surface for the first insulative film, and including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient; and
(c) depositing a second insulative film for protecting the first conductor film against oxidation on the first insulative film and the wirings, and then depositing a third insulative film on the second insulative film by a chemical vapor deposition method using an oxygen-containing gas.
In the preferred embodiment, the step (b) includes:
a step of depositing the first conductor film and the second conductor film successively on the first insulative film including the inside of the wiring opening;
a step of polishing the first and the second conductor films, thereby forming wirings in the wiring opening; and
a step of selectively etching to remove the upper portion of the wirings to render the upper surface of the wirings lower than the upper surface of the first insulative film.
Preferably, the step (b) includes:
a step of depositing the first conductor film and the second conductor film successively on the first insulative film including the inside of the wiring opening;
a step of polishing the first conductor film and the second conductor films thereby forming wirings in the wiring opening; and
a step of selectively etching to remove the upper portion of the wirings to render the upper surface of the wirings higher than the upper surface of the first insulative film.
This invention provides, as sixth embodiment, a method of manufacture of a semiconductor device comprising the following steps of:
(a) forming a wiring opening to a first insulative film deposited on a wafer;
(b) forming wirings in the wiring opening, the wirings including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient;
(c) applying a reducing plasma processing to the wirings; and
(d) depositing, after the step (c), a second insulative film for protecting the first conductor film against oxidation on the first insulative film and the wirings, and then depositing a third insulative film by a chemical vapor deposition method using an oxygen-containing gas on the second insulative film.
In the preferred embodiment, the reducing plasma processing is a plasma processing in an ammonia gas atmosphere. Also, the reducing plasma processing may be a plasma processing in a hydrogen gas atmosphere. Preferably, the reducing plasma processing has a step of applying plasma processing in a hydrogen gas atmosphere and a step of applying plasma processing in an ammonia gas atmosphere.
After the reducing plasma processing, the second insulative film and the third insulative film are deposited on the first insulative film and the wirings continuously without opening to the atmospheric air.
This invention provides, as a seventh feature, a method of manufacture of a semiconductor device comprising the following steps of:
(a) forming a wiring opening to a first insulative film deposited on a wafer;
(b) forming wirings in the wiring opening, the wirings including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient; and
(c) depositing a second insulative film for protecting the first conductor film against oxidation on the first insulative film and the wirings, and then depositing a third insulative film by a chemical vapor deposition method using an oxygen-containing gas on the second insulative film;
wherein the step of forming the first insulative film has a step of depositing a seventh insulative film having a first dielectric constant and a step of depositing an eighth insulative film having a second dielectric constant higher than the first dielectric constant on the seventh insulative layer, and wherein the second insulative film is deposited on the eighth insulative film.
In the preferred embodiment, the seventh insulative film comprises an organic insulative film of a lower dielectric constant than the silicon oxide film, and the eighth insulative film comprises a silicon oxide film.
This invention provides, as an eighth feature, a method of manufacture of a semiconductor device comprising the following steps of:
(a) forming a wiring opening to a first insulative film deposited on a wafer;
(b) forming wirings in the wiring opening, the wirings including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient; and
(c) depositing a second insulative film for protecting the first conductor film against oxidation on the first insulative film and the wirings, and then depositing a third insulative film by a chemical vapor deposition method using an oxygen-containing gas on the second insulative film;
wherein the step of forming the first insulative film has a step of depositing an organic insulative film having a lower dielectric constant than the silicon oxide film, and wherein the second insulative film is deposited on the organic insulative film.
This invention provides, as a ninth feature, a semiconductor device comprising:
(a) a wiring opening formed to a first insulative film;
(b) wirings disposed to bury the inside of the wiring opening and including a first conductor film having a barrier property to block the diffusion of copper and a second conductor film comprising copper as a main ingredient;
(c) a second insulative film for protecting the first conductor film against oxidation formed on the first insulative film and the wiring; and
(d) a third insulative film comprising a silicon oxynitride film laminated on the second insulative film.
In the preferred embodiment, the second insulative film comprises a silicon nitride film. The second insulative film may also comprise a silicon carbide film or a silicon carbonitride film. Preferably, the thickness of the second insulative film is less than the third insulative film. Preferably, a step is formed between the height for the upper surface of the wirings and the height for the upper surface of the first insulative film. Preferably, the height for the upper surface of the wirings is higher than the height for the upper surface of the first insulative film. On the other hand, the height for the upper surface of the wirings may be lower than the height for the upper surface of the first insulative film.